On Car

WS1 Petrol Fuel Injector Testing

        

Make Toyota  Model 1zz

1. First we listened to the injectors as the engine was idling. Next we used a long screwdriver to hear the injectors. They should sound like a sharp tap, not a dull thud or nothing.
OK ✓ Not OK ..........

Can you get to all the injectors? Yes ✓ No .........

Comments: All the injectors were good and could hear them open and close because they made Small tapping noise

2. Next we Checked you have battery voltage to the injectors so they can work.

Record battery voltage: 12.8v

Record voltage at each injector you can get to by back probing. Be

careful to not puncture or damage wiring.

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
12.8v	12.8v	12.8v	12.8v	-	-	Volts

3. With the engine idling, we watched the injector firing by using an LED tester .We Hooked up the test light and connected the tip to pin that has back probed connector to injector -. As the injector is grounded by the ECM to fire, the test light should also be grounded to fire, and will flash.

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
✓	✓	✓	✓	-	-	Tick if flashes OK

4.        With the engine idling, we watched the injector firing by using a multi-meter and set it to read % (duty cycle). We Recorded the readings for each cylinder at idle in the boxes below.

       

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
4.8%	4.7%	4.7%	4.7%	-	-	Duty cycle %

5.        With the multi-meter we set it to read % (duty cycle),then we accelerate the engine with short, fast throttle openings , and note in the boxes below the maximum % reading you can get on the multi-meter: note the RPM.

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
8.6%	7.9%	8.3%	8.4%	-	-	Duty cycle %

RPM + - 2000

6.       We Set the multi-meter to read Hz, and with the engine idling, we recorded the readings for each cylinder in the boxes below:

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
0.31	0.28	0.30	0.30	-	-	Hz

7.        With the multi-meter we set it to read Hz, we  increased the engine RPM, and watched how the Hz changes.Next we Record our highest reading in the boxes below:

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
0.45	0.50	0.54	0.52	-	-	kHz

The Injector

­A fuel injector is  like a electronically controlled valve , it is supplied fuel by the fuel pump inside the car, and it is capable of opening and closing many times per second. It provides the right amount of fuel to make the car run, it is run by the engine control unit (ECU) is equipped with a whole lot of sensors.

Inside a fuel injector

When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel  to make as fine a mist as possible so that it can burn easily.

A fuel injector firing

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.

Fuel injectors mounted in the intake manifold of the engine

The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.

In this picture, you can see three of the injectors. The fuel rail is the pipe on the left.

http://auto.howstuffworks.com/fuel-injection3.htm
http://www.youtube.com/watch?v=eVCYR4B7IZ8

Chart of Inputs and Outputs

  

We Measured the signals with a multimeter.

Coolant Temperature (THW or ECT) DC volts	Cold engine                 3.074v	Warmed-up engine                    1.286
Throttle Position Sensor DC volts	Closed throttle 0.574V	Open throttle 3.89v
Crank or RPM sensor AC volts and Hertz	Idle rpm AC volts = 2V Hertz = 40Hz	2500 rpm AC volts = 7V Hertz = 60Hz
MAP sensor DC volts	Idle vacuum 0.530	No vacuum or key on engine off     1.382
Air Temperature (THA or IAT) DC volts	Cold engine 3.22v	Warmed-up engine 3.22v
Throttle Position Switch (Idle and/or WOT) DC volts	Closed throttle 0.574v	Open throttle   3.89v
CAM sensor AC volts & Hertz	Idle rpm AC volts = 2.04 Hertz = 0.338Hz	2500 rpm AC volts = 4.05 Hertz = 0.635Hz
Fuel Injector Duty cycle %	Idle 2.6% for all the Injectors	Acceleration 1)8.6         2)8.4 3)8.3         4)8.5
Idle Air Control Duty cycle %	Idle 35.8%	Cranking or 2500 Had a aftermarket Link ECU

                     Input Sensors and Actuators On -Vehicle

Make: Toyota      Model : 1 ZZ

First we Located the fuel injector , it will be on the thorttle body of the engine.
Next we Back-probe the wire to the fuel injector by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside.
Don’t puncture or damage the wiring. We Hooked up the multimeter red lead to read dc volts and the black lead is grounded.
Record the voltage to the fuel injector: 14v

Discuss why would we bother checking the voltage supply to the fuel injectors? So we know that the injectors are firing properly and there is low resistance in the injector circuit so they function as normal. If there was high resistance the injectors would be getting low voltage therefore it would be operating poorly .

If we find a lower voltage at the injectors than at battery , what can that mean ? And how would the injector operation be affected ?

The injectors could have a high resistance causing it to get low voltage , the injecters would have poor operation and getting lack of fuel .Draw a full circuit diagram for the fuel injectors, including battery ,ignition switch, main relay and how the injectors are switched:

Reference Voltage at TPS sensor

What is the purpose of the reference voltage to the throttle postion sensor?
So the ECU knows when the throttle is open or closed and gets the right signal.

What could cause problems so that there is not the correct reference voltage at the throttle position sensor ?
Dirt/ Dust inside the TPS giving a higher resistance , this can cause poor engine performance and poor fuel economy.

                                                Ground at TPS sensor

First we locate the Earth/Ground wire on the TPS.
Next we Back-probe the sensor ground or earth wire by inserting a pin down therubber insulation far enough to connect with the metal wire terminal on theinside. Then we Hook up the multimeter red lead to read dc volts. Set the meter range or scale to 4V or less and  the meter black lead is grounded on engine block or battery.
Record the voltage on the meter 0.00V (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)
We does this voltage tell you about the ECU earth or ground ? why is it important to measure it ?
That the conection is good and there is no resistance in the wires makes it a good connection  , we measure it because we have to find out the correct voltage to the ECU

Discuss what could go wrong so that the ECU earth or ground is not good.
There could be corrosion on the terminals giving false readings

                                         Throttle Position Sensor return/output:

With the engine NOT running, we back-probe a wire for the TPS input by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Do not damage the wiring. Then we Set up the voltmeter to read DC Volts. Attach meter red lead to the pin; attach black lead to a good ground.

Record the reading from the meter. 0.574 If you do not get a reading on the meter, you may have to check for a good connection, or try different wires until you get a good reading to record above.

Open the throttle to about the half open position, (make sure engine isnot running) and record the reading on the meter 2.3v 
Close the throttle. 

Open the throttle to the full open position, (make sure engine is not running), and record the reading on the meter: 2.910v 

Close the throttle.

Slowly open the throttle from the closed position to the full open position,and watch that the meter readings slowly increase with no sudden jumps or gaps in the signal. Ok

Describe how the TPS works.
A TPS sensor is an important in a car because it tells the ECU when the throttle is open or closed , it indicates how much air is coming in. The TPS has a viper arm which is connected to the throttle vavle , as the valve opens the resistance changes to tell the ECU what postition the throttle is then the ECU controls the fuel injection and changes the engine rpm and power. If the TPS is faulty it will idle at a higher rpm because of the wrong resistance and output voltages and the engine wouldnt run properly.
Draw a full circuit diagram for the TPS on this vehicle:

ECT (Engine Coolant Temperature) Sensor

We had a NTC  (Negative Temperature Coefficient Thermistor) Type ECTWith the engine Not running,we back-probe a likely wire for the ECT supply by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Then we Set up the voltmeter to read DC Volts. Attach meter red lead to the pin; attach black lead to a good ground.

Record the reading from the meter: 3.65v

Is the engine cold, between cold and normal temperature (warming up), or
at normal operating temperature? Cold

Does the voltage reading above seem right for the temperature of the
engine? (yes or no) Yes 
Make sure all students and meter leads are clear of the engine. Start the
engine. Let the engine warm up for about two more minutes, and record
the voltage of the ECT sensor now: 1.44v

A warmer engine should usually show a lower voltage. Is the reading
above lower than the first reading? (yes or no) Yes

Describe how an ECT sensor works.

As the tempurature increases inside the engine the resistance in the thermistor goes down.It sends the information to the ECU which controls the fuel injection, ignition timing, idling speed and automatic transmission timing.This is because the engine needs to run rich when it is cold.

Describe how the ECT sensor voltage affects the fuel injection output from the ECU.

When the engine is cold the ECU grounds the injectors for longer to make a rich Air/Fuel mixture due to the condensation of the engine being cold. So when the engine is warmed up the RPM will drop and less fuel being used as the mixture is lean.

  Ground Coolant Temperature Sensor
Record the voltage on the meter: 0.00v (A good ground will usually read less than 0.05V. Some manufacturers say 0.10V.)

What does this voltage tell you about the ECU earth or ground ? Why is it important to measure ?

So there is a good connection to earth and no voltage is used up and the ECU gets the correct reading. If there was a fault it would send the ECU false reading this is because the voltage is lost as it is trying to push the current through the wires.

Draw the circuit diagram for the ECT sensor for this vehicle. Include some detail inside the ECU.

                     RPM Sensor or Crank Position Sensor (CKP):

With the engine Not Running, we back-probe a RPM signal wire by inserting a pin down the rubber insulation far enough to connect with the metal wire terminal on the inside. Do Not damage the wiring.

Next we Set up the voltmeter to read AC volts. Then we Attach the red lead to the pin; attach black lead to a good ground.

Record the reading from the meter: 6.23v If you do not get a reading on the meter, you may have to check for a good connection, or try another wire. Turn off the engine when you switch to another wire, then restart
the engine and check for a reading. Try different wires, or get help from your Lecturer until you get a good reading to record above.

Increase engine RPM to about 2500 rpm. Record the reading from the meter: 8.08vReturn the engine to idle speed. Switch the voltmeter to read DC volts.
Record the reading from the meter: 1.112v

Increase engine RPM to about 2500 rpm. Record the reading from the meter: 1.42v Return the engine to idle speed.

Describe how this type of RPM or Crank sensor works:
The crank sensor measures the engine speed or the engine's RPM , this information is then sent to the ECU which turns on the fuel injectors. This is a really important sensor without the engine will have difficulty starting.

What can go wrong so the ECU did not receive the correct signal from the RPM or Crank sensor:
If the ECU doesnt get the correct reading the injectors wouldnt be firing at the correct time and the ECU will not receive the correct information so the engine will crank but it wont start. This can be cause by corrosion on the terminals , or loose connection/ Broken wire


MAP or MAF Sensor:

The engine had a aftermarket link ECU
With the engine not running we had 1.833v and at IDLE we had 0.373v then we did a short acceleration and got 0.72v

Describe how the MAP sensor works to tell the engine how much air comes inside the engine ?
A high vaccum at ilde means that there is high resistance in the MAP sensor so low voltage is sent back to the ECU . As the vaccum decreases with the throttle opening , resistance decreases and the output voltage increases

Discuss how the readings above are correct or incorrect for this engine :
It is correct and there is low voltage at idle & high voltage with key on , engine off. If the ECU did not recieve the correct signal from the MAP sensor it could be a vaccum leak